Veins employed as bypass grafts and arteries exposed to hypertension develop thickened walls. The veins also develop intimal hyperplasia. The purpose of the proposed study is to identify the mechanical parameter which best correlates with wall thickening. Deformations and stresses in the circumferential, longitudinal and radial directions, as well as shear stresses will be manipulated. A first set of experiments will be performed to determine the course of development of wall thickening over time. Double side-to-side anastamoses will be performed between the femoral artery and femoral vein bilaterally. An algorithm then will be followed in order to isolate the mechanical parameters which best correlate with maximum and with minimum wall thickening. These experiments will employ a) restrictive cuffs around the grafts, b) stretching of the grafts, c) limiting the pressure delivered to the grafts. These techniques will be employed as dictated by the algorithm. A final set of experiments will be performed to evaluate reversibility of wall thickening. In all experiments grafts will be removed when mature, and will be studied histologically. These experiments may indicate a means of preventing graft thickening. It is hoped that these experiments will indicate the mechanical parameter associated with wall thickening, and will suggest a means of preventing thickening.